Base station device and channel assigning method

ABSTRACT

Priority order storage section  113  stores the order of priority for an uplink and the reverse order of priority for a downlink. Channel allocation section  114  performs channel allocation for a downlink in the order of priority of the downlink stored in priority order storage section  113 , based on the CIR of the downlink. In addition, channel allocation section  114  performs channel allocation for an uplink in the order of priority of the uplink stored in priority order storage section  113 , based on the CIR of the uplink. It is thereby possible to perform reuse partitioning in asymmetrical data communications.

TECHNICAL FIELD

The present invention relates to a base station apparatus and channelallocation method in a cellular system, wherein the respective channelsare allocated to either an uplink or a downlink.

BACKGROUND ART

As illustrated in FIG. 1, generally, the entire service area is dividedinto a plurality of cells, and one base station apparatus is installedfor each cell in a mobile communication system. Then, the respectivecellular station apparatuses perform wireless communication with theirown base station apparatuses, to which they belong.

In the case of FIG. 1, since cellular station apparatus 31 and 32 belongto cell 11, they perform wireless communication with base stationapparatus 21 installed in cell 11. Similarly, since cellular stationapparatus 33 belongs to cell 12, it performs wireless communication withbase station apparatus 22 installed in cell 12.

Here, respective cellular station apparatuses transmit uplink signalsand receive downlink signals using the channel allocated by their basestation apparatuses. A plurality of channel allocation methods of amobile communication system using this cellular system has beenpreviously proposed.

One of the channel allocation methods is described in Toshihito Kanai:“Autonomous Reuse Partitioning Dynamic Channel Allocation Method inMicro Cell Mobile Communication System (ARP),” The Technical Report ofIEICE, RCS91-32 (1991). With this Autonomous Reuse Partitioning (ARP)system, a channel is selected with the same order of priority in allcells, and among the selected channels, the one with a CIR (Carrier toInterference Ratio) exceeding the predetermined threshold is usedsequentially.

Channel allocation in the conventional ARP system is next explainedusing the flowchart illustrated in FIG. 2.

First, when there is a call request at Step (hereinafter referred to as“ST”) 51, the base station apparatus measures the desired wave level ofthe uplink, and the cellular station apparatus measures the desired wavelevel of the downlink at ST52.

Then, at ST 53, the base station apparatus selects the available channelwith the highest priority according to the common order of priority forall base station apparatuses. An available channel denotes an unusedslot in the case of the TDMA system, and in the case of the CDMA/TDDsystem it denotes an unallocated slot or a slot wherein uplink/downlinkto be allocated is matched and that has available code resource.

Next, at ST54, the base station apparatus measures the interference wavelevel of the uplink for the selected channel, and the cellular stationapparatus measures the interference wave level of the downlink.

Then at ST55, the base station apparatus compares the uplink/downlinkCIR of the selected channel with a predetermined threshold (theso-called channel search.) If the uplink CIR and downlink CIR exceed thethreshold, the base station apparatus will allocate a call to theselected channel at ST 56. However, if either uplink CIR or downlink CIRare below the threshold, the base station apparatus will determinewhether or not available channels are unchecked with the channel search(hereinafter, referred to as “non-searched channel”) at ST 57.

If non-searched channels still remain, the base station apparatus andcellular station apparatus repeat the processes following ST 53,excluding the channels completed for a channel search. Meanwhile, ifnon-searched channels do not remain, the base station apparatus willcomplete the processing as call loss at ST59.

With ARP channel allocation, it is possible to perform the so-calledreuse partitioning (Halpern:“Reuse Partitioning in Cellular Systems,”Proc. of VTC '83, pp. 322–327 (1983)) in each cell in an autonomous,spreading manner, wherein the optimal cell reuse factor can be set foreach channel depending on the distance from the cellular stationapparatus to the base station apparatus, that is, the size of the lossof the transmission path.

Furthermore, by performing reuse partitioning and setting the optimalcell reuse factor, the system is capable of accommodating more calls asa whole.

With this conventional ARP system, it is assumed that the number ofchannels for an uplink and downlink is fixed at the same number and thata pair of uplink channel and downlink channel is fixed. Therefore,uplink/downlink to be allocated to each channel is common to all cells.For example, in FIG. 1 above, cellular station apparatus 33 does nottransmit signals in the channel where cellular station apparatus 31receives signals. Thus, a cellular station apparatus is not disrupted bysignals transmitted from the cellular station apparatus that belongs toanother cell.

However, it is expected that asymmetrical data communications, whereinthe information volume of the downlink is significantly larger than thatof the uplink, will be common place in the future. With thisasymmetrical data communication, each channel is allocated to an uplinkor downlink in a flexible manner. Namely, it is necessary to change thenumber of channels allocated to the uplink and downlink from thepredetermined number of channels.

However, if the conventional ARP channel allocation method were appliedto asymmetrical data communication and channel allocation were performedin the same order of priority for an uplink and downlink, theuplink/downlink to be allocated to each channel would likely differdepending on the cell. In this condition, a cellular station apparatuswould be disrupted by signals transmitted from the cellular stationapparatus belonging to another cell, and it would therefore beimpossible to perform reuse partitioning.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a base stationapparatus and channel allocation method for performing reusepartitioning in asymmetrical data communications, and for determiningthe number of channels of the uplink/downlink in a flexible manner.

The present invention achieves the above object by performing channelallocation for an uplink and downlink individually, according to anorder of priority that is common to all base station apparatuses andthat is reversed between an uplink and a downlink.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a mobilecommunication system;

FIG. 2 is a flowchart to explain the conventional channel allocationoperation;

FIG. 3 is a block diagram illustrating a schematic configuration of thebase station apparatus according to the first embodiment of the presentinvention;

FIG. 4 is a block diagram illustrating a schematic configuration of thecellular station apparatus performing wireless communication with thebase station apparatus, according to the first embodiment of the presentinvention;

FIG. 5 is a diagram to explain a frame configuration of asymmetricaldata communication according to the first embodiment of the presentinvention;

FIG. 6 is a diagram illustrating one example of the order of priority ofthe uplink and downlink according to the first embodiment of the presentinvention;

FIG. 7 is a flowchart to explain the channel allocation operation of theuplink of the base station apparatus according to the first embodimentof the present invention;

FIG. 8 is a flowchart to explain the channel allocation operation of thedownlink of the base station apparatus according to the first embodimentof the present invention.

FIG. 9 is a diagram illustrating one example of the order of priority ofthe uplink and downlink, according to the second embodiment of thepresent invention; and

FIG. 10 is a diagram to explain a frame configuration of asymmetricaldata communications according to the second embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described specificallybelow with reference to accompanying drawings.

(First Embodiment)

FIG. 3 is a block diagram illustrating a schematic configuration of thebase station apparatus according to the first embodiment of the presentinvention. FIG. 4 is a block diagram illustrating a schematicconfiguration of the cellular station apparatus performing wirelesscommunication with the base station apparatus of FIG. 3.

In addition, the base station apparatus illustrated in FIG. 3 and thecellular station apparatus illustrated in FIG. 4 apply to a mobilecommunication system using a CDMA/TDD system. With a CDMA/TDD system,the wireless communication link channel is specified by time slots andcode.

In the base station apparatus illustrated in FIG. 3, control signalmultiplier 101 multiplies the transmission data by control signals, suchas pilot signals and channel allocation information. Channel allocationinformation shows to which time slot and code a local station callchannel are allocated.

Coding/modulation section 102 performs the predetermined coding andmodulation processing on output signals of control signal multiplier101. Spreading section 103 performs spreading processing on outputsignals of coding/modulation section 102, using the spreading signalspecified in the instruction from the channel allocation section 114.

Transmission RF section 104 performs the predetermined wirelessprocessing on output signals of spreading section 103 in the time slotspecified in the instruction from the channel allocation section 114.

Common apparatus 105 switches over from transmission to reception orvice versa to perform wireless communication using the same antenna. Itwirelessly transmits output signals of transmission RF section 104 fromantenna 106, and outputs the signals received at antenna 106 toreception RF section 107.

Reception RF section 107 performs the predetermined wireless processingon output signals of common apparatus 105 in the time slot specified inthe instruction from the channel allocation section 114.

Reverse spreading section 108 performs reverse spreading processing onoutput signals of reception RF section 107 using the spreading codespecified in the instruction from the channel allocation section 114,and separates a desired wave from an interference wave.Demodulation/decode section 109 performs demodulation processing anddecode processing on output signals of reverse spreading section 108.

Separation section 110 separates control signals and received data fromoutput signals of demodulation/decode section 109, and outputsinformation about the reception power of the desired wave of thedownlink and the reception power of the interference wave of thedesignated time slot, which are included in control signals, to CIRcalculation section 112. In addition, if a control signal includesinformation about a communication request, separation section 110 willnotify reception power measurement section 111 and channel allocationsection 114 of said information.

Reception power measurement section 111 measures the reception power ofthe desired wave and the reception power of the interference wave of thedesignated time slot, and outputs the measurement results to CIRcalculation section 112.

CIR calculation section 112 calculates the CIR of a downlink based oninformation about the reception power of the desired wave andinterference wave output from separation section 110, and calculates theCIR of an uplink based on the respective reception power of the desiredwave and interference wave, which is measured at reception powermeasurement section 111.

Priority order storage section 113 stores the order of priority of theslots to be checked with channel research for an uplink and downlinkrespectively. The detailed relationship between the order of priority ofthe uplink and that of the downlink will be described below.

Channel allocation section 114 performs channel allocation for thedownlink based on the CIR of the downlink, according to the order ofpriority of the downlink stored in priority order storage section 113.Also, channel allocation section 114 performs channel allocation for theuplink based on the CIR of the uplink, according to the order ofpriority of the uplink stored in priority order storage section 113.

Also, channel allocation section 114 controls spreading section 103 andtransmission RF section 104 according to the results of the channelallocation of the downlink, and controls reception RF section 107 andreverse spreading section 108 according to the results of the channelallocation of the uplink. In addition, channel allocation section 114outputs channel allocation information to control signal multiplier 101.The channel allocation operation will be described in detail below.

Meanwhile, in the cellular station apparatus illustrated in FIG. 4,control signal multiplier 201 multiplies the transmission data bycontrol signals. Control signals to be multiplied by control signalmultiplier 201 include pilot signals, the reception power of the desiredwave of the downlink, the reception power of the interference wave ofthe designated time slot or information about the call request.

Coding/modulation section 202 performs the predetermined codingprocessing and modulation processing on output signals of control signalmultiplier 201. Spreading section 203 performs spreading processing onoutput signals of coding/modulation section 202, using the spreadingcode specified in the instruction from the channel control section 212.

Transmission RF section 204 performs the predetermined wirelessprocessing on output signals of spreading section 203 in the time slotspecified in the instruction from the channel control section 212.

Common apparatus 205 changes over from transmission to reception or viceversa to perform wireless communication using the same antenna. Itwirelessly transmits output signals of the transmission RF section 204from antenna 206, and outputs the signals received at antenna 206 toreception RF section 207.

Reception RF section 207 performs the predetermined wireless processingon output signals of common apparatus 205 in the time slot specified inthe instruction from the channel control section 212.

Reverse spreading section 208 performs reverse spreading processing onoutput signals of reception RF section 207, using the spreading codespecified in the instruction from the channel control section 212, andseparates the desired waves from the interference waves.

Demodulation/decode section 209 performs demodulation processing anddecode processing on the output signals of reverse spreading section208. Separation section 210 separates the control signals and receiveddata from the output signals of demodulation/decode section 209, andoutputs the channel allocation information included in control signalsto channel control section 212.

Reception power measurement section 211 measures the respectivereception power of the desired wave and the interference wave separatedat reverse spreading section 208, and outputs the measurement results tocontrol signal multiplier 201.

Channel control section 212 controls spreading section 203, transmissionRF section 204, reception RF section 207 and reverse spreading section208 based on channel allocation information.

The relationship between the order of priority of the uplink and that ofthe downlink will be next explained using FIG. 5 and FIG. 6 according tothe embodiments of the present invention.

FIG. 5 is a diagram to explain a frame configuration of asymmetricaldata communication according to the embodiments of the presentinvention. In FIG. 5, wireless frame 301 is divided into time slot #0 to#14. In the case of asymmetrical data communication, it should bepossible to perform an allocation for either an uplink or a downlink ineach time slot.

Therefore, it is necessary to set an order of priority for a channelsearch for all time slots in an uplink and a downlink. FIG. 6 shows anexample of an order of priority of the uplink and downlink according tothe embodiments of the present invention.

As illustrated in FIG. 6, the order of priority of the uplink isopposite to the order of priority of the downlink, according to theembodiments of the present invention. Namely, with the order of priorityof the uplink, time slot #0 with the smallest slot number has thehighest priority, and as the slot number increases, the priority becomeslower. In contrast, with the order of priority of the downlink, timeslot #14 with the largest slot number has the highest priority, and asthe slot number decreases, the priority becomes lower.

Channel allocation operation of the base station apparatus illustratedin the above FIG. 3 will be next explained using FIG. 7 and FIG. 8.

FIG. 7 is a flowchart to explain the channel allocation operation of theuplink according to the embodiments of the present invention. FIG. 8 isa flowchart to explain the channel allocation operation of the downlinkaccording to the embodiments of the present invention. Also, the orderof priority of FIG. 6 shall apply to FIG. 7 and FIG. 8.

In FIG. 7, when a call request is made from the cellular stationapparatus at ST501, reception power measurement section 111 measures thereception power of the desired wave of the uplink at ST502.

In addition, at ST503 and ST504, channel allocation section 114 selectstime slot #0 with the highest priority for the uplink, according to theorder of priority illustrated in FIG. 6.

Next, at ST505, reception power measurement section 111 measures thereception power of the interference wave for time slot #0 of the uplink,and CIR calculation section 112 calculates CIR.

Then, at ST506, channel allocation section 114 compares the CIR of timeslot #0 of the uplink with the predetermined threshold (the so-calledchannel search.) If the CIR of time slot #0 of the uplink is larger thanthe threshold, channel allocation section 114 will allocate the call totime slot #0 at ST507. In contrast, if the CIR of time slot #0 of theuplink is less than the threshold, channel allocation section 114 willselect time slot #1 with the second highest priority at ST508, ST509 andST504. Time slot #1 is then processed at ST505 and ST506.

Hereafter, processing from ST504 to ST509 is repeated until the timeslot with an uplink CIR larger than the threshold is found. Then, if theCIR of the uplink is below the threshold in all time slots, the basestation apparatus will complete processing as call loss at ST510.

Meanwhile, in FIG. 8, when a call request is made at ST601, separationsection 110 obtains information about the reception power of the desiredwave of the downlink at ST602.

Also, at ST603 and St604, channel allocation section 114 selects timeslot #14 with the highest priority for the downlink, according to theorder of priority illustrated in FIG. 6.

Next, at ST605, separation section 110 obtains information about thereception power of the interference wave for time slot #14 of thedownlink, and CIR calculation section 112 calculates the CIR.

Then, at ST606, channel allocation section 114 compares the CIR of timeslot #14 of the downlink with the predetermined threshold (the so-calledchannel search.)

If the CIR of time slot #14 of the downlink is larger than thethreshold, channel allocation section 114 will allocate the call to timeslot #14 at ST607. On the other hand, if the CIR of time slot #14 of thedownlink is less than the threshold, channel allocation section 114 willselect time slot #13 with the second highest priority at ST608, ST609and ST604. Then, time slot #13 is processed at ST605 and ST606.

Hereafter, processing from ST604 to ST609 is repeated sequentially untila time slot with a downlink CIR exceeding the threshold is found. Then,if the CIR of the downlink is below the threshold in all time slots, thebase station apparatus will complete processing as call loss at ST610.

As described, by reversing the order of priority of the uplink to thatof the downlink, it is unlikely that uplink/downlink to be allocated toeach time slot will differ depending on the cell. It is thereby toperform reuse partitioning in the case of applying ARP to asymmetricaldata communications.

(Second Embodiment)

The second embodiment applies to performing open loop transmission powercontrol in an uplink, that is, at a cellular station apparatus using aTDD system. In the case of performing open loop transmission powercontrol for an uplink, the cellular station apparatus measures thereception power of the known signals accumulated in the downlink reportchannel. In addition, the base station apparatus reports informationabout transmission power of the report channel, so the cellular stationapparatus estimates the transmission path loss by obtaining saidinformation and subtracting reception power from the transmission power.Since the uplink carrier and downlink carrier are identical with a TDDsystem, the cellular station apparatus transmits signals with a poweradding transmission path loss to the target reception power, and it ispossible for the base station apparatus to receive signals with optimalpower.

However, since communication quality is subject to changes by the minutefor reasons such as changes in the cellular station apparatus, when openloop transmission power control is implemented, it is preferable thatthe slot of the report channel and the slot of the uplink are close intime.

Thus, according to the embodiments of the present invention, the orderof priority of an uplink is specified to perform a channel search for anuplink sequentially from a time slot immediately after the reportchannel. In addition, the order of priority of a downlink is specifiedto perform a channel search in reverse order to the uplink, startingwith a slot before the slot of the report channel and closer in time. Inthis embodiment of the present invention, the configurations of the basestation apparatus and cellular station apparatus are the same as in FIG.3 and FIG. 4 described in the above first embodiment of the presentinvention, and the explanations are omitted.

FIG. 9 is a diagram illustrating one example of the order of priority ofthe uplink and downlink according to the embodiments of the presentinvention. In FIG. 9, assuming that the report channel is assigned timeslot #7, with the order of priority of the uplink, time slot #8 has thehighest priority, and subsequently up to time slot #14, as the slotnumber increases, the order of priority becomes lower. Further, fromtime slot #0 to time slot #6, as the slot number increases, the order ofpriority becomes lower. On the other hand, with the order of priority ofthe downlink, time slot #6 has the highest priority, and subsequently upto time slot #0, as the slot number decreases, the order of prioritybecomes lower. Further, from time slot #14 to time slot #8, as the slotnumber decreases, the order of priority becomes lower.

FIG. 10 is a diagram to explain a frame configuration of asymmetricaldata communications according to the embodiments of the presentinvention, and it shows the state after a call is allocated. In FIG. 10,with wireless frame 701, the report channel is assigned time slot #7,the uplink is assigned time slot #8 to #12, the downlink is assignedtime slot #2 to #6, and neither link is assigned other time slots.

If channel allocation is implemented according to the order of priorityin FIG. 9 above, as illustrated in FIG. 10, in wireless frame 701, theuplink and the downlink are allocated separately, divided by time slot#7 assigned to the report channel.

Thus, by reversing the order of priority of the uplink to that of thedownlink, using the slot assigned the report channel as a base, openloop transmission power control can be taken into account in addition tothe effect of a first embodiment of the present invention.

As described above, according to the present invention, it is possibleto perform reuse partitioning in the case of applying ARP toasymmetrical data communications, and further, open loop transmissionpower control can be taken into account.

This application is based on Japanese Patent Application No. 2000-188350filed on Jun. 22, 2000, the entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is suitable for the base station apparatuses usedfor a micro cell mobile communication system utilizing Autonomous ReusePartitioning Dynamic Channel Allocation Method.

1. A base station apparatus that allocates channels to time slots by anautonomous reuse partitioning dynamic channel allocation method, theapparatus comprising: a channel allocator that performs: (1) a channelsearch for an uplink according to a predetermined order of priority, (2)a channel search for a downlink according to an order of priorityreverse to said predetermined order of priority for the uplink, and (3)a channel allocation for the uplink and downlink in accordance withresults of the uplink and downlink channel searches; a receiver thatreceives signals through the allocated uplink channel; and a transmitterthat transmits signals through the allocated downlink channel, wherein:the base station apparatus is used in a TDD mobile communication system,and the channel allocator performs the channel search for the uplinksequentially from a slot that is placed after a slot assigned to areport channel and close in time.
 2. A channel allocation method for anautonomous reuse partitioning dynamic channel allocation system, themethod comprising: performing a channel search for an uplink accordingto a predetermined order of priority; performing a channel search for adownlink according to an order of priority reverse to said predeterminedorder of priority for the uplink; and allocating a channel for theuplink and downlink in accordance with results of the uplink anddownlink channel searches, wherein: the method is used in a TDD mobilecommunication system, and the channel search for the uplink is performedsequentially from a slot that is placed after a slot assigned to areport channel and close in time.